Combination spring and gas filled accumulator

Abstract

A compact fluid accumulator both stores a relatively large amount of fluid and provides good fluid pressure stability. The accumulator includes a piston slidably disposed in a cylinder having a fluid inlet/outlet at one end which communicates with a first chamber and one face of the piston. Engaging the opposite face of the piston, and disposed in a second chamber, is a compression spring. The second chamber is filled with a gas which is at atmospheric pressure when the accumulator is relaxed. When pressurized hydraulic fluid fills the first chamber, the piston moves against the pressure of the spring and gas in the second chamber. The present invention thus provides an accumulator having the relatively small size of a gas filled accumulator without the leakage problem of a super-atmospheric gas charge—the extra force being provided by the compression spring.

1. A hydraulic fluid supply system comprising, in combination,
 a sump, 
 a suction line disposed in said sump, 
 a pump having a inlet in fluid communication with said suction line and an outlet in fluid communication with an outlet line, 
 a pressure relief valve in fluid communication with said outlet line, 
 an accumulator, 
 a check valve only permitting fluid flow from said outlet line to said accumulator, 
 another check valve only permitting fluid flow from said accumulator to said outlet line and 
 a solenoid valve in series with said another check valve, 
 said accumulator including a housing defining a cylinder and having an inlet/outlet port at one end, 
 a piston disposed in said cylinder having a circumferential channel and an O-ring seal disposed in said channel and defining a first, fluid chamber in fluid communication with said inlet/outlet port and a second, gas chamber, and 
 a compression spring and a gas disposed in said second, gas chamber for biasing said piston toward said first, fluid chamber. 
 
     
     
       2. The hydraulic fluid supply system of  claim 1  further including a pressure transducer in fluid communication with said outlet line. 
     
     
       3. The hydraulic fluid supply system of  claim 1  wherein said compression spring is a coil spring. 
     
     
       4. The hydraulic fluid supply system of  claim 1  wherein said gas in said second chamber is at substantially atmospheric pressure when the first chamber is exhausted. 
     
     
       5. The hydraulic fluid supply system of  claim 1  wherein said compression spring has a spring constant of between about 20 newtons/meter and 28 newtons/meter. 
     
     
       6. A spring biased and gas filled accumulator assembly for hydraulic systems comprising, in combination,
 a cylindrical housing defining a cylinder and having an inlet/outlet port at one end, 
 a piston slidably disposed in said cylinder, having two opposed faces, a circumferential channel and an O-ring seal disposed in said channel for sealing between said piston and said cylinder and defining a first, fluid chamber adjacent one face of said piston in fluid communication with said inlet/outlet port and a second, gas chamber adjacent another of said faces, 
 a compression spring and a gas disposed in said second, gas chamber for biasing said piston toward said first, fluid chamber, 
 a first fluid circuit communicating with said inlet/outlet port and disposed in parallel with a second fluid circuit, said first fluid circuit including a first check valve and an orifice and said second fluid circuit including a solenoid valve and a second check valve. 
 
     
     
       7. The accumulator assembly or  claim 6  wherein said first check valve inhibits fluid flow away from said inlet/outlet port of said accumulator and permits fluid flow toward said inlet/outlet port of said accumulator. 
     
     
       8. The accumulator assembly or  claim 6  wherein said second check valve inhibits fluid flow toward said inlet/outlet port of said accumulator and permits fluid flow away from said inlet/outlet port of said accumulator.